What is the effect of Aspirin on Uric Acid levels?

Effect of Aspirin on Uric Acid Levels

Low-dose aspirin (≤325 mg daily) causes modest uric acid retention by decreasing renal uric acid excretion, but this effect is not clinically significant enough to warrant discontinuation when used for cardiovascular prophylaxis. 1

Mechanism of Action

Aspirin affects uric acid handling in the kidneys through a dose-dependent, bimodal effect:

• Low doses (75-325 mg/day): Decrease uric acid excretion and clearance, leading to mild uric acid retention 2
• High doses (>3 g/day): Produce uricosuric effects, increasing uric acid excretion

This occurs because aspirin:

• Competes with uric acid for renal tubular secretion at low doses
• Inhibits tubular reabsorption of uric acid at high doses

Clinical Evidence

Research demonstrates that even mini-dose aspirin affects uric acid handling:

• 75 mg/day aspirin decreases uric acid excretion by approximately 15% 2
• Both 60 mg/day and 300 mg/day aspirin decrease fractional excretion of uric acid, with 300 mg/day significantly decreasing uric acid clearance 3
• Low-dose aspirin (≤325 mg/day) increases the risk of recurrent gout attacks by 81% compared to no aspirin use, with stronger effects at lower doses (OR=1.91 for ≤100 mg) 4

However, more recent research suggests minimal long-term effects:

• A 2021 study found no significant correlation between taking low-dose aspirin (50-100 mg/day) for more than one month and serum uric acid levels or fractional excretion of uric acid in elderly patients 5

Clinical Implications

Despite these effects on uric acid handling, the American College of Rheumatology specifically recommends:

• Do not discontinue low-dose aspirin (≤325 mg daily) when used for cardiovascular prophylaxis in gout patients 1
• The relative risks attributable to the modest effects of low-dose aspirin on serum urate are considered negligible in gout management 1

Special Considerations

1. Renal function:

   • Short-term low-dose aspirin may affect renal function in elderly patients, with effects potentially persisting up to 3 weeks after discontinuation 6
   • Consider monitoring renal function in elderly patients on aspirin therapy

2. Gout management:

   • Concomitant use of allopurinol may nullify the detrimental effect of aspirin on gout attacks 4
   • Consider urate-lowering therapy dose adjustment in patients with gout who require low-dose aspirin

3. Dosage considerations:

   • Lower aspirin doses (60 mg/day) show less suppressive effect on renal function than higher doses (300 mg/day) and may be preferable for long-term use 3

Practical Recommendations

1. Continue low-dose aspirin when indicated for cardiovascular prophylaxis, despite its modest effects on uric acid levels
2. Monitor uric acid levels and renal function in patients at risk for gout or with pre-existing renal impairment
3. Consider lower aspirin doses (60-75 mg/day) when possible, especially in elderly patients
4. Adjust urate-lowering therapy as needed in patients with gout who require low-dose aspirin therapy

In summary, while aspirin does cause modest uric acid retention at low doses, this effect is not clinically significant enough to outweigh its cardiovascular benefits when indicated.